Method and apparatus for controlling motor, washing machine, and method of controlling the washing machine

ABSTRACT

A method and apparatus for controlling a motor, a washing machine, and a method of controlling the washing machine that efficiently calculate an amount of laundry within a drum are provided. The method of controlling a washing machine that calculates an amount of laundry housed within a drum rotating by a motor, the method includes: accelerating the drum from a first rotation speed to a second rotation speed by enabling the motor to apply torque to the drum in a predetermined direction and decelerating the drum from the second rotation speed to the first rotation speed by enabling the motor to apply torque to the drum in an opposite direction; and calculating the laundry amount from the sum of currents applied to the motor at the accelerating of the drum.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of PCT Application No. PCT/KR2011/002183 filed on Mar. 30, 2011, which claims priority to Korean Application Nos. 10-2010-0028667 filed in Korea on Mar. 30, 2010 and 10-2010-0038637 filed in Korea on Apr. 26, 2010, the entirety of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for controlling a motor, a washing machine, and a method of controlling the washing machine, and more particularly, to a method and apparatus for controlling a motor, a washing machine, and a method of controlling the washing machine that efficiently calculate an amount of laundry within a drum.

2. Related Art

In general, washing machines are an apparatus for washing through a process such as wash, rinse, and dehydration in order to remove a contamination material stuck to clothes and bedclothes (hereinafter, referred to as ‘laundry’) using water and detergent and a mechanical operation.

The washing machines are classifies into an agitator type washing machine, a pulsator type washing machine, and a drum type washing machine.

The agitator type washing machine washes laundry by laterally rotating a wash rod standing at the center of a wash tub, the pulsator type washing machine washes laundry using a frictional force between water and laundry by laterally rotating a rotation blade of a circular plate shape formed in a lower part of a wash tub, and the drum type washing machine washes laundry by injecting water, detergent, and laundry into a drum and rotating the drum.

In the drum washing machine, a tub for housing washing water is mounted within a cabinet forming an external appearance, and a drum for housing laundry is disposed within the tub, and a motor for rotating the drum is mounted at the rear side of the tub, and a drive shaft connected to the rear side of the tub by penetrating though the tub is installed at the motor. A lift is mounted within the drum, and when the drum rotates, the lift lifts laundry.

In such a washing machine, a phenomenon in which laundry are leaned to one side by entangled laundry occurs and thus eccentricity in which one side is heavy based on the center of the drum occurs. When the drum rotates with a high speed (e.g., when dehydrating laundry) in an eccentric state of laundry, due to unbalance in which a geometrical center of a rotation shaft of the drum and an actual center of gravity do not correspond, a vibration and noise occurs. In order to reduce such a vibration and noise, an apparatus for reducing unbalance of the drum is installed, and the apparatus is referred to as a balancer.

A counter weight that corrects eccentricity by attaching an additional weight has been used as a balancer for a drum washing machine, but nowadays, ring-shaped space having a predetermined width in a circumferential direction is formed at a front surface or a rear surface of the drum, and a ball balancer that is completely sealed by inserting the ball into the space, charging the space with liquid, and performing thermal fusion-bonding is generally used. When the drum rotates with a high speed, an internal material of the ball balancer is distributed to move to the side opposite to the center of gravity of laundry and thus the center of gravity of the drum approaches a rotation center.

A washing machine using such a balancer measures a rotation speed change amount of a drum after rotating the drum with a predetermined speed before rotating the drum with a high speed, thereby measuring an unbalance degree of the drum. By measuring an unbalance degree of the drum, when the balancer is disposed at an appropriate position, the drum is accelerated. That is, an appropriate acceleration time point is determined according to an unbalance degree of the drum, and the drum is accelerated. Therefore, in order to measure an unbalance degree of the drum, it is required to constantly rotate a motor with a desired rotation speed. Further, there is a problem that it is difficult for a washing machine using a balancer to measure an amount of laundry within a drum.

SUMMARY OF THE INVENTION

An aspect of the present invention is to provide a method and apparatus for controlling a motor, a washing machine, and a method of controlling the washing machine that relatively accurately calculate an amount of laundry within a drum regardless of a change by other factors.

The object of the present invention is not limited to the above-described objects and the other objects will be understood by those skilled in the art from the following description.

In accordance with an aspect of the present invention, a method of controlling a washing machine that calculates an amount of laundry housed within a drum rotating by a motor, the method includes: accelerating the drum from a first rotation speed to a second rotation speed by enabling the motor to apply torque to the drum in a predetermined direction and decelerating the drum from the second rotation speed to the first rotation speed by enabling the motor to apply torque to the drum in an opposite direction; and calculating the laundry amount from the sum of currents applied to the motor at the accelerating of the drum.

In accordance with another aspect of the present invention, a washing machine includes: a rotatable drum that houses laundry; a motor that rotates the drum; a motor driver that controls the motor by applying a current to the motor to accelerate the drum from a first rotation speed to a second rotation speed by enabling the motor to apply torque to the drum in a predetermined direction and to decelerate the drum from the second rotation speed to the first rotation speed by enabling the motor to apply torque to the drum in an opposite direction; and a laundry amount calculation unit that calculates an amount of laundry housed to the drum from the sum of currents in which the motor driver applies to the motor.

ADVANTAGEOUS EFFECTS

A method and apparatus for controlling a motor, a washing machine, and a method of controlling the washing machine according to the present invention have the following effects.

First, even when unbalance of a drum is large, a motor can constantly rotate with a desired rotation speed.

Second, in order to enable a rotation speed of the motor to approach an instruction speed to correspond to a rotation speed change of the motor according to an unbalance degree of the drum, an instruction voltage value can be applied.

Third, after a compensated instruction voltage value is stored by comparing an instruction speed and a present rotation speed, when the instruction speed is input again, by outputting the compensated instruction voltage value, the present rotation speed can rapidly approach the instruction speed.

Fourth, by maintaining a rotation speed adjacent to 108 rpm, which is a preferable rotation speed that measures an unbalance degree of a drum, an unbalance degree of the drum can be efficiently measured.

Fifth, when calculating a laundry amount, by repeating acceleration and deceleration of the drum with a speed in which laundry stick to the drum and rotate, an error generating due to a fall of laundry can be minimized.

Sixth, by decelerating and accelerating the drum by applying torque to the drum, a change factor by a friction of laundry other than a balancer can be minimized.

Seventh, by accelerating and decelerating the drum with acceleration of the same magnitude, a laundry amount can be calculated with only the sum of currents applied to the motor.

Eighth, by quickly repeating acceleration and deceleration of the drum, an error can be minimized.

Effects of the present invention are not limited to the above-described effects and the other effects will be understood by those skilled in the art from a description of claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary embodiment of the present invention will be described in detail with reference to the following drawings in which like numerals refer to like elements.

FIG. 1 is a perspective view illustrating a washing machine according to an exemplary embodiment of the present invention;

FIG. 2 is a cross-sectional view illustrating the washing machine of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of a motor control device according to an exemplary embodiment of the present invention;

FIG. 4 is a flowchart illustrating a method of controlling a motor according to an exemplary embodiment of the present invention;

FIG. 5 is a graph illustrating a rotation speed and a PWM signal change according to a time in a motor control device according to an exemplary embodiment of the present invention;

FIG. 6 is a block diagram illustrating a configuration of a washing machine according to an exemplary embodiment of the present invention;

FIG. 7 is a graph illustrating a rotation speed of a motor to a time when calculating a laundry amount of a washing machine according to an exemplary embodiment of the present invention;

FIG. 8 is a diagram illustrating unbalance of a drum when calculating a laundry amount of a washing machine according to an exemplary embodiment of the present invention;

FIG. 9 is a graph illustrating a rotation speed of a motor to a time when calculating a laundry amount in a method of controlling a washing machine according to an exemplary embodiment of the present invention; and

FIG. 10 is a graph illustrating a rotation speed of a motor to a time when calculating a laundry amount of a washing machine according to another exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Like reference numerals designate like elements throughout the specification.

Hereinafter, a method and apparatus for controlling a motor, a washing machine, and a method of controlling the washing machine according to an exemplary embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view illustrating a washing machine according to an exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating the washing machine of FIG. 1.

A washing machine 100 according to an exemplary embodiment of the present invention includes a cabinet 111 that forms an external appearance, a door 112 that opens and closes one side of the cabinet 111 to inject laundry into the cabinet 111, a tub 122 that is disposed at the inside of the cabinet 111 and that is supported by the cabinet 111, a drum 124 that is disposed at the inside of the tub 122 and that inserts laundry and that rotates, a motor 113 that applies torque to the drum 124 to rotate the drum 124, a detergent box 133 that houses detergent, and a control panel 114 that receives a user input and that displays a state of the washing machine 100.

A laundry injection hole 120 for injecting and ejecting laundry is formed in the cabinet 111.

In order to open and close the laundry injection hole 120, the door 112 is rotatably coupled to the cabinet 111. The control panel 114 is provided in the cabinet 111.

The detergent box 133 is withdrawably provided at the cabinet 111.

The tub 122 is disposed to absorb a shock by a spring 115 and a damper 117 within the cabinet 111. The tub 122 houses washing water. The drum 124 is disposed at the inside of the tub 122.

The drum 124 houses laundry and rotates. The drum 124 has a plurality of penetration holes to pass through washing water. A lift (not shown) for lifting laundry to a predetermined height when the drum 124 rotates is disposed at an inner wall of the drum 124. The drum receives torque by the motor 113 and rotates.

A balancer 126 is provided at a periphery of the drum 124 and adjusts the center of gravity of the drum 124 when laundry are in an eccentric state. When laundry are in an eccentric state and the drum 124 rotates, due to unbalance in which a geometrical center of a rotation shaft of the drum 124 and an actual center of gravity do not correspond, a vibration and noise occurs. The balancer 126 reduces unbalance of the drum 124 by enabling the actual center of gravity of the drum 124 to approach a rotation center.

The balancer 126 may be disposed at the front side and/or the rear side of the drum 124, and in the present exemplary embodiment, the balancer 126 is disposed at the front side of the drum 124. When the drum 124 rotates, laundry housed within the drum 124 are generally gathered at the inside, i.e., the rear side of the drum 124 and thus in order to balance with laundry gathered at the rear side of the drum 124, it is preferable that the balancer 126 is provided at the front side of the drum 124.

The balancer 126 includes a material having a predetermined weight at the inside so that the center of gravity may variably move, and the balancer 126 is formed to include a path that the material can move in a circumferential direction. In the balancer 126, as the internal material thereof is distributed to move to the side opposite to the center of gravity of laundry, the center of gravity of the drum 124 approaches a rotation center.

The balancer 126 may include a liquid balancer including liquid having a predetermined weight at the inside or a ball balancer including a ball having a predetermined weight. In the present exemplary embodiment, the balancer 126 includes a charging fluid together with a ball therein.

A gasket 128 seals the tub 122 and the cabinet 111. The gasket 128 is disposed between an inlet of the tub 122 and the laundry injection hole 120. The gasket 128 prevents washing water in the tub 122 from being leaked to the outside while relieving a shock transferred to the door 112 when the drum 124 rotates. A circulation nozzle 127 for injecting washing water into the drum 124 is provided at the gasket 128.

The motor 113 rotates the drum 124. The motor 113 rotates the drum 124 with various speeds or directions. The motor 113 includes a stator 113 a in which a coil is wound and a rotor 113 b that rotates by performing an electromagnetic interaction with a coil.

A plurality of wound coils are provided at the stator 113 a. A plurality of magnets that perform an electromagnetic interaction with a coil are provided at the rotor 113 b. The rotor 113 b rotates by an electromagnetic interaction of a coil and a magnet, and rotary power of the rotor 113 b is transferred to the drum 124 to rotate the drum 124.

A hole sensor 113 c for measuring a position of the rotor 113 b is provided at the motor 113. The hole sensor 113 c generates an on/off signal by a rotation of the rotor 113 b. A speed and a position of the rotor 113 b are estimated through an on/off signal generated in the hole sensor 113 c.

Detergent such as wash detergent, a fiber conditioner, or bleach is housed at the detergent box 133. It is preferable that the detergent box 133 is withdrawably provided at a front surface of the cabinet 111. Detergent within the detergent box 133 is injected into the tub 122 by mixing with washing water when washing water is supplied.

It is preferable that a water valve 131 for adjusting injection of washing water from an outside water source, a water flow path 132 for enabling washing water injected into the water valve 131 to flow to the detergent box 133, and a water pipe 134 for injecting washing water mixed with detergent in the detergent box 133 into the tub 122 are provided within the cabinet 111.

It is preferable that a drainpipe 135 for ejecting washing water within the tub 122, a pump 136 for ejecting washing water within the tub 122, a circulation flow path 137 for circulating washing water, a circulation nozzle 127 for injecting washing water into the drum 124, and a drain flow path 138 for draining washing water to the outside are provided within the cabinet 111. According to an exemplary embodiment, the pump 136 includes a circulating pump and a drain pump, and the circulating pump and the drain pump are connected to the circulation flow path 137 and the drain flow path 138, respectively.

An input unit 114 b for receiving an input of various operation commands such as wash course selection or an operating time and reservation on each stroke basis through a user and a display unit 114 a for displaying an operation state of the washing machine 100 are provided in the control panel 114.

Operation of the washing machine 100 according to an exemplary embodiment of the present invention will be described.

After a user opens the door 112 and injects laundry into the drum 124, by manipulating the control panel 114, the washing machine 100 operates. When the washing machine 100 operates, a wash stroke that removes a contamination material from laundry by soaking laundry in washing water in which wash detergent is mixed and rotating the drum 124, a rinse stroke that removes remaining wash detergent of laundry by soaking laundry in washing water in which a fiber conditioner is mixed and rotating the drum 124, and a dehydration stroke that dehydrates laundry by rotating the drum 124 with a high speed are sequentially performed. Water supply, wash, rinse, drain, dehydration, and dry are performed in the respective strokes.

Dehydration is to rotate the drum 124 with a high speed to dehydrate laundry soaked in washing water and is performed at a wash stroke, a rinse stroke, and a dehydration stroke. When dehydration is performed, the drum 124 rotates about 400 rpm or more, greatly about 1,000 rpm, and thus when unbalance of the drum 124 is large, vibration and noise largely occurs.

Therefore, when dehydration is started, by constantly maintaining a rotation speed of the motor 113 and measuring an unbalance degree of the drum 124, when the balancer 126 is at an appropriate position, the motor 113 is accelerated. That is, an appropriate acceleration time point is determined according to an unbalance degree of the drum 124, and the motor 113 is accelerated. It is preferable that a rotation speed for measuring an unbalance degree of the drum 124 is 108 rpm, which is a maximum velocity in which laundry stick to the drum 124 and rotate and in which noise and vibration does not largely occur.

FIG. 3 is a block diagram illustrating a configuration of a motor control device according to an exemplary embodiment of the present invention.

Referring to FIG. 3, a motor control device according to an exemplary embodiment of the present invention includes a motor controller 230, a pulse width modulation (PWM) calculation unit 240, an inverter 250, a current sensor 260, and an unbalancing sensor 270.

The motor controller 230 controls power input to the motor 113. The motor controller 230 includes a voltage controller 239, a speed/position detection unit 231, a speed controller 233, a current controller 235, and a coordinate converter 237.

The voltage controller 239 outputs an instruction voltage value to an instruction speed. The voltage controller 239 stores an instruction voltage value to each experimentally obtained instruction speed.

It is preferable that the voltage controller 239 stores an instruction voltage value to an instruction speed according to a rotation direction of the drum 124. Further, the voltage controller 239 stores each instruction voltage value to an instruction speed according to a laundry amount housed in the drum 124.

The voltage controller 239 stores a d-axis instruction voltage value and a q-axis instruction voltage value on a d-q axis rotation coordinate system defined by a d-axis parallel to a magnetic flux direction and a q-axis orthogonal to a magnetic flux direction of a permanent magnet, and when an instruction speed is requested, the voltage controller 239 outputs the d-axis instruction voltage value and the q-axis instruction voltage value to the coordinate converter 237. As described in the following description, by newly storing an instruction voltage value to an instruction speed, when the same instruction speed is input, the voltage controller 239 outputs a newly stored instruction voltage value.

The coordinate converter 237 converts a d-q axis rotation coordinate system and an uvw fixed coordinate system. The coordinate converter 237 converts an instruction voltage value that is input to a d-q axis rotation coordinate system to a three-phase instruction voltage value. Further, the coordinate converter 237 converts a present current of a fixed coordinate system sensed by the current sensor 260 to be described later to a d-q axis rotation coordinate system. The coordinate converter 237 receives an input of a position θ of the rotor 113 b detected by the speed/position detection unit 231 to be described later and converts a coordinate system.

The PWM calculation unit 240 receives an input of a signal of an uvw fixed coordinate system that is output from the motor controller 230 and generates a PWM signal. The inverter 250 receives an input of a PWM signal from the PWM calculation unit 240 and directly controls power that is input to the motor 113. The current sensor 260 senses a present current that is output from the inverter 250. According to an exemplary embodiment, the PWM calculation unit 240 may be included in the inverter 250.

The speed/position detection unit 231 detects rotation speed and a position of the rotor 113 b of the motor 113. The speed/position detection unit 231 detects a rotation speed and a position of the rotor 113 b by a position of the rotor 113 b sensed by the hole sensor 113 c. According to an exemplary embodiment, the speed/position detection unit 231 may detect a rotation speed of the motor 113 through a current sensed by the current sensor 260.

The speed controller 233 generates each of a d-axis instruction current value and a q-axis instruction current value on a d-q axis rotation coordinate system so that a rotation speed of the rotor 113 b detected in the speed/position detection unit 231 follows an instruction speed by performing a proportional-integral-differential (PID) control.

When the rotation speed of the rotor 113 b detected by the speed/position detection unit 231 is maintained while having some fluctuation, the speed controller 233 compares an average value of a changing value with the instruction speed.

The current controller 235 generates each of a d-axis instruction voltage value and a q-axis instruction voltage value by a PID control of a present current sensed by the current sensor 260.

The unbalancing sensor 270 measures an unbalance degree of the drum 124 through a rotation speed of the rotor 113 b detected by the speed/position detection unit 231. The unbalancing sensor 270 measures an unbalance degree of the drum 124 by measuring a rotation speed change amount of the rotor 113 b.

When the drum 124 rotates with a predetermined speed, if the drum 124 is unbalanced, the rotation speed of the rotor 113 b has some fluctuation, and the unbalancing sensor 270 measures an unbalance degree through a change amount of rotation speed of the rotor 113 b. The unbalancing sensor 270 measures an unbalance degree with a difference between a rotation speed change amount of the rotor 113 b and a previously stored reference speed change amount. The reference speed change amount is differently stored according to a laundry amount. Because a difference between a rotation speed change amount of the rotor 113 b and a reference speed change amount sequentially changes, the unbalancing sensor 270 calculates an average of a maximum value and a minimum value of a difference between a rotation speed change amount of the rotor 113 b and the reference speed change amount as an unbalance value.

When the unbalancing sensor 270 measures an unbalance degree, it is preferable that the drum 124 rotates with laundry stuck thereto and rotates with a maximum velocity in which noise and vibration does not greatly occur, and in the present exemplary embodiment, and the drum 124 rotates with 108 rpm.

Hereinafter, operation of a motor control device according to an exemplary embodiment of the present invention will be described with reference to FIG. 4.

FIG. 4 is a flowchart illustrating a method of controlling a motor according to an exemplary embodiment of the present invention.

A first power value is applied to the motor 113 based on a first instruction voltage value Vd*Nq* corresponding to an instruction speed ω* (S310). The instruction speed ω* is a speed in which the drum 124 should maintain when the unbalancing sensor 270 measures an unbalance degree of the drum 124, and in the present exemplary embodiment, the instruction speed ω* is 108 rpm.

When the instruction speed ω* for sensing an unbalance degree of the drum 124 is input, the voltage controller 239 outputs a previously stored d-axis first instruction voltage value Vd* and a q-axis first instruction voltage value Vq* to the coordinate converter 237.

The coordinate converter 237 converts a first instruction voltage value Vd*Nq* that is input to a d-q axis rotation coordinate system to a three-phase instruction voltage value and outputs the three-phase instruction voltage value to the PWM calculation unit 240, the PWM calculation unit 240 generates a first PWM signal corresponding to the first instruction voltage value Vd*/Vq* converted to an uvw fixed coordinate system. The inverter 250 receives an input of a first PWM signal from the PWM calculation unit 240 and applies a first power value to the motor 113.

When the first power value is applied to the motor 113, the motor 113 rotates while maintaining a first rotation speed ω (S320). The first rotation speed ω is an average value of a rotation speed having some fluctuation. When the first power value is applied to the motor 113, the motor 113 accelerates and arrives at a speed adjacent to the instruction speed ω*. In this case, when unbalance of the drum 124 is large, a rotation speed of the drum 124 maintains a first rotation speed ω smaller than an instruction speed ω*.

A second power value is applied to the motor 113 based on a compensated second instruction voltage value Vd**/Vq** according to a difference between the first rotation speed ω and the instruction speed ω* (S330). When the motor 113 rotates while maintaining the first rotation speed ω, the speed/position detection unit 231 detects a rotation speed of the rotor 113 b and transfers the rotation speed to the speed controller 233. The speed controller 233 compares the first rotation speed ω, which is a an average value of a rotation speed detected by the speed/position detection unit 231 with the instruction speed ω*.

In this case, after the motor 113 maintains a predetermined rotation speed, the speed controller 233 uses an average value of a rotation speed detected by the speed/position detection unit 231 after about 3 to 5 seconds after a predetermined rotation speed is input to receive a stabilized rotation speed as a first rotation speed ω and compares the average value with the instruction speed ω*.

The speed controller 233 generates each of a d-axis second instruction current value Id** and a q-axis second instruction current value Iq** by performing a PID control so that the first rotation speed ω follows the instruction speed ω*. The current controller 235 outputs each of a d-axis second instruction voltage value Vd** and a q-axis second instruction voltage value Vq** to the coordinate converter 237 by performing a PID control of a second instruction current value Id**/Iq** generated by the speed controller 233 and a present current Id/Iq in which the current sensor 260 senses and converted to a d-q axis rotation coordinate system in a coordinate converter.

The coordinate converter 237 converts a second instruction voltage value Vd**Nq** that is input to a d-q axis rotation coordinate system to a three-phase instruction voltage value and outputs the three-phase instruction voltage value to the PWM calculation unit 240, and the PWM calculation unit 240 generates a second PWM signal corresponding to a second instruction voltage value Vd**/Vq** converted to an uvw fixed coordinate system.

The inverter 250 receives an input of a second PWM signal from the PWM calculation unit 240 and applies a second power value to the motor 113.

When the second power value is applied to the motor 113, the motor 113 rotates while maintaining a second rotation speed ω, and the second instruction voltage value Vd**/Vq** is stored as a first instruction voltage value Vd*/Vq* (S340). The second rotation speed is an average value of a rotation speed having some fluctuation, similarly to the first rotation speed ω.

When the second power value is applied to the motor 113, the motor 113 rotates while maintaining a second rotation speed ω′ adjacent to the instruction speed ω* further than the first rotation speed ω.

The voltage controller 239 receives an input of a second instruction voltage value Vd**/Vq** that is output by the current controller 235 and stores the second instruction voltage value Vd**/Vq** as the first instruction voltage value Vd*/Vq* corresponding to the instruction speed ω*. Therefore, after dehydration is performed in a washing stroke, when dehydration is again performed in a rinse stroke and a dehydration stroke, if an instruction speed ω* is again input to sense an unbalance degree of the drum 124, the voltage controller 239 outputs a newly stored first instruction voltage value Vd*/Vq*.

When the motor 113 rotates while maintaining a second rotation speed, the voltage controller 239 detects unbalance of the drum 124 based on a rotation speed change amount of the motor 113 (S350). When the motor 113 rotates while maintaining a second rotation speed, if the drum 124 is unbalanced, a rotation speed of the rotor 113 b has some fluctuation, and the unbalancing sensor 270 measures an unbalance degree through a change amount of a rotation speed of the rotor 113 b detected by the speed/position detection unit 231.

The unbalancing sensor 270 measures an unbalance degree with a difference between a rotation speed change amount of the rotor 113 b and a previously stored reference change amount. The reference speed change amount is differently stored according to a laundry amount. Because a difference between the rotation speed change amount of the rotor 113 b and the reference speed change amount sequentially changes, the unbalancing sensor 270 calculates an average of a maximum value and a minimum value of a difference value between the rotation speed change amount of the rotor 113 b and the reference speed change amount as an unbalance value.

When the motor controller 230 accelerates the motor 113 at an appropriate acceleration time point according to an unbalance degree of the drum sensed by the unbalancing sensor 270, a wash step, in which the drum 124 rotates with a high speed, such as dehydration is performed.

FIG. 5 is a graph illustrating a rotation speed and a PWM signal change according to a time in a motor control device according to an exemplary embodiment of the present invention.

When the inverter 250 receives an input of a first PWM signal from the PWM calculation unit 240 and applies a first power value to the motor 113, the motor 113 accelerates and arrives at a speed adjacent to an instruction speed ω*. When unbalance of the drum 124 is large, a rotation speed of the drum 124 maintains a first rotation speed ω smaller than the instruction speed ω*.

When the inverter 250 receives an input of a second PWM signal from the PWM calculation unit 240 and applies a second power value to the motor 113, the motor 113 rotates while maintaining a second rotation speed ω′ adjacent to the instruction speed ω*.

Therefore, even when unbalance of the drum 124 is large, the motor controller 230 rotates the motor 113 with a rotation speed adjacent to an instruction speed ω* for measuring an unbalance degree of the drum 124. When the motor 113 rotates while maintaining the second rotation speed ω′, the motor controller 230 measures unbalance and controls the motor 113 based on the unbalance.

In the foregoing description, an output of a second instruction voltage value from a first rotation speed is not limited to the present exemplary embodiment. The second instruction voltage value may be calculated by an appropriate compensation equation or various control methods.

FIG. 6 is a block diagram illustrating a configuration of a washing machine according to an exemplary embodiment of the present invention.

A motor driver 310 controls the motor 113 by applying power to the motor 113. The motor driver 310 is formed with various electronic elements such as a switching element that enables appropriate power to be applied to the motor 113 by controlling input power. The motor driver 310 controls the motor 113 with a current control method that controls a rotation of the motor 113 by changing a current applied to the motor 113. The motor driver 310 includes the motor controller 230, the PWM calculation unit 240, the inverter 250, and the current sensor 260, except for the speed/position detection unit 231 shown in FIG. 3, and the motor driver 310 may exclude some element according to an exemplary embodiment.

In order to measure an amount of laundry housed in the drum 124, the motor driver 310 enables the motor 113 to generate torque in a predetermined direction by applying power to the motor 113 and then enables the motor 113 to generate torque in an opposite direction by applying power to the motor 113. The motor driver 310 controls the motor 113 to accelerate and decelerate the drum 124. A detailed description thereof will be described with reference to FIGS. 7 and 8.

A speed/position detection unit 330 detects rotation speed and a position of the rotor 113 b of the motor 113. The speed/position detection unit 330 detects a rotation speed and a position of the rotor 113 b by a position of the rotor 113 b sensed by the hole sensor 113 c. The speed/position detection unit 330 corresponds to the speed/position detection unit 231 shown in FIG. 3. The speed/position detection unit 330 detects a rotation speed of the motor 113 through a current sensed by the current sensor 260.

A rotation speed and a position of the rotor 113 b detected by the speed/position detection unit 330 are output to the motor driver 310, and the motor driver 310 performs a current control that changes a current applied to the motor 113 based on the rotation speed and the position.

A laundry amount calculation unit 350 calculates an amount of laundry housed within the drum 124 from a current in which the motor driver 310 applies to the motor 113 when the motor 113 accelerates and decelerates the drum 124. A detailed description thereof will be described with reference to FIGS. 4 and 5.

FIG. 7 is a graph illustrating a rotation speed of a motor to a time when calculating a laundry amount of a washing machine according to an exemplary embodiment of the present invention, and FIG. 8 is a diagram illustrating unbalance of a drum when calculating a laundry amount of a washing machine according to an exemplary embodiment of the present invention.

Referring to FIG. 7, when calculating a laundry amount, after the motor 113 accelerates the drum 124 from a first rotation speed ω₀ to a second rotation speed ω₁ by generating torque in a predetermined direction, the motor 113 decelerates the drum 124 from the second rotation speed ω to the first rotation speed ω₀ by generating torque in an opposite direction. In this case, acceleration a that accelerates the drum 124 and acceleration −α that decelerates the drum 124 have the same magnitude. When the motor 113 decelerates the drum 124 from the second rotation speed ω₁ to the first rotation speed ω₀, the motor 113 performs inverse braking that decelerates by generating torque in an opposite direction.

Hereinafter, a segment in which the motor 113 accelerates the drum 124 from the first rotation speed ω₀ to the second rotation speed ω₁ with a predetermined acceleration a from t₀ to t₁ is referred to as an acceleration segment, and a segment in which the motor 113 decelerates from the second rotation speed ω to the first rotation speed ω₀ with a predetermined acceleration −α from t₁ to t₂ is referred to as a deceleration segment.

The second rotation speed ω₁ and the first rotation speed ω₀ are a speed in which laundry stick to the drum 124 and rotate, and in the present exemplary embodiment, the second rotation speed ω₁ is 120 rpm, which is a maximum velocity in which noise and vibration does not greatly occur, even if an unbalance degree of the drum 124 is large, and the first rotation speed ω₀ is 70 rpm, which is a minimum speed in which laundry stick to the drum 124 and rotates. Further, it is preferable that the acceleration α is 20 rpm/s.

When the motor driver 310 applies a current i and a voltage e to the motor 113, torque T of the motor 113 is as follows.

$\begin{matrix} {T_{d} = {{\frac{1}{\omega}{e \cdot i}} = {k\; i}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \end{matrix}$

where ω is a rotation speed of the motor 113, and k is a constant.

That is, in a current control, because a voltage e in which the motor driver 310 applies to the motor 113 is constant, torque T of the motor 113 is proportional to a current i.

In an acceleration segment of FIG. 5( a), torque T_(d) ^(u) of the drum 124 is as follows.

T _(u) ^(d) =Jα+T _(f) +T _(ball) −mgr cos θ  [Equation 2]

In this case, J is the center of gravity of the balancer 126 and laundry within the drum 124, i.e., moment of inertia to an unbalance weight of the drum 124, and T_(f) is torque by a friction (e.g., friction of laundry) other than the balancer 126, and T_(ball) is torque by a friction of the balancer 126. m is an unbalance weight of the drum 124, and r is a distance from the center of the drum 124 to the center of gravity of unbalance of the drum 124, and 0 is an angle to the center of gravity of unbalance of the drum 124.

In a deceleration segment of FIG. 5( b), torque T_(d) ^(d) of the drum 124 is as follows.

T _(d) ^(d) =Jα+T _(f) −T _(ball) −mgr cos θ  [Equation 3]

When calculating a laundry amount from Equations 1 and 2, in an acceleration segment and a deceleration segment of the drum 124, total energy is as follows.

$\begin{matrix} {{{\int_{t_{0}}^{t_{1}}T_{d}^{u}} - {\int_{t_{1}}^{t_{2}}T_{d}^{d}}} = {{\int_{t_{0}}^{t_{2}}{J\; \alpha \; {\theta}}} + {\int_{t_{1}}^{t_{2}}{T_{ball}{\; \theta}}} + {\int_{t_{0}}^{t_{1}}{T_{f}{\; \theta}}} - {\int_{t_{1}}^{t_{2}}{T_{f}{\theta}}} - {\int_{t_{0}}^{t_{1}}{{mgr}\; \cos \; \theta \; {\; \theta}}} + {\int_{t_{1}}^{t_{2}}{{mgr}\; \cos \; \theta \; {\; \theta}}}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack \end{matrix}$

It is assumed that a torque T_(ball) by a friction of the balancer 126 is proportional to a relative velocity between the balancer 126 and the drum 124, and a relative velocity is proportional to acceleration.

T _(ball) ≈J _(b)α  [Equation 5]

where J_(b) is the moment of inertia of the balancer 126.

In Equation 5, Equation 4 is as follows.

∫_(t) ₀ ^(t) ² Jαdθ+∫ _(t) ₀ ^(t) ² T _(ball) dθ=α(θ₂−θ₀)(J+J _(b))  [Equation 6]

In Equation 4, it is assumed that energy dissipation by a friction is the same in an acceleration segment and a deceleration segment of the drum 124.

∫_(t) ₀ ^(t) ¹ T _(f) dθ−∫ _(t) ₁ ^(t) ² T _(f) dθ=0  [Equation 7]

In Equation 4, when laundry are dried laundry that are not soaked by washing water, an unbalance weight of the drum 124 may be ignored, and when laundry are wet laundry soaked by washing water, the rotation number of the drum 124 increases by integer times in an acceleration segment and a deceleration segment.

−∫_(t) ₀ ^(t) ¹ mgr cos θdθ+∫ _(t) ₁ ^(t) ² mgr cos θdθ=0  [Equation 8]

In an acceleration segment and a deceleration segment of Equation 4, total energy is represented by Equations 6 to 8.

∫_(t) ₀ ^(t) ¹ T _(d) ^(u)−∫_(t) ₁ ^(t) ² T _(d) ^(d)=α(θ₂−θ₀)(J+J _(b))  [Equation 9]

In an acceleration segment, energy is represented by Equation 1.

$\begin{matrix} {{\int_{t_{0}}^{t_{1}}{T_{d}^{u}{\int_{t_{0}}^{t_{1}}{k\; i\; \alpha \; t\; {t}}}}} \approx {k\; \Delta \; \theta {\sum\limits_{t = t_{0}}^{t_{1}}i}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack \end{matrix}$

In a deceleration segment, energy is represented by Equation 1.

$\begin{matrix} {{\int_{t_{0}}^{t_{1}}T_{d}^{d}} \approx {k\; \Delta \; \theta {\sum\limits_{t = t_{1}}^{t_{2}}i}}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack \end{matrix}$

In an acceleration segment and a deceleration segment, total energy is represented by Equations 10 and 11.

$\begin{matrix} {{{\int_{t_{0}}^{t_{1}}T_{d}^{u}} - {\int_{t_{1}}^{t_{2}}T_{d}^{d}}} \approx {k\; \Delta \; {\theta \left( {{\sum\limits_{t = t_{0}}^{t_{1}}i} - {\sum\limits_{t = t_{1}}^{t_{2}}i}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack \end{matrix}$

Total moment of inertia is represented by Equations 9 and 12.

$\begin{matrix} {{J + J_{b}} = \frac{k\; \Delta \; {\theta \left( {{\sum\limits_{t = t_{0}}^{t_{1}}i} - {\sum\limits_{t = t_{1}}^{t_{2}}i}} \right)}}{\alpha \left( {\theta_{2} - \theta_{0}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack \end{matrix}$

In Equation 13, total moment of inertia is proportional to the sum of currents applied at an acceleration segment and the sum of currents applied at a deceleration segment, and a change amount Δθ and a difference θ₂−θ₀ of an angle to the center of gravity of unbalance of the drum 124 are approximate values that may be cancelled.

Therefore, through an experiment of various laundry amounts, after accelerating the drum 124 from a first rotation speed ω₀ to a second rotation speed ω₁, when decelerating the drum 124 from the second rotation speed ω₁ to the first rotation speed ω₀, if the sum of applied currents is written with a profile, a laundry amount may be calculated through the profile.

When calculating a laundry amount, laundry sticks to the drum 124 and rotates and thus a change amount Δθ and a difference θ₂−θ₀ of an angle to the center of gravity of unbalance of the drum 124 may be calculated from a position of the motor 113 detected by the speed/position detection unit 330. Therefore, in order to calculate an accurate laundry amount, a profile including a change amount Δθ and a difference θ₂−θ₀ of an angle to the center of gravity of unbalance of the drum 124 is written, a laundry amount may be calculated through the profile.

When the laundry amount calculation unit 350 stores the profile and the motor 113 accelerates and decelerates the drum 124, the motor driver 310 calculates a laundry amount from the profile by calculating the sum of currents applied to the motor 113. Further, the laundry amount calculation unit 350 may calculate a laundry amount through a profile from the sum of currents in which the motor driver 310 applies to the motor 113 and a position of the motor 113 detected by the speed/position detection unit 330.

FIG. 9 is a graph illustrating a rotation speed of a motor to a time when calculating a laundry amount in a method of controlling a washing machine according to an exemplary embodiment of the present invention.

When calculating a laundry amount, if the motor driver 310 applies power to the motor 113, the motor 113 accelerates the drum 124 from a first rotation speed ω₀ to a second rotation speed ω₁ by generating torque in a predetermined direction. When a rotation speed of the drum 124 arrives at the second rotation speed ω₁, the motor driver 310 inverse brakes the motor 113, and the motor 113 decelerates the drum 124 from the second rotation speed ω₁ to the first rotation speed ω₀, by generating torque in an opposite direction.

The motor driver 310 controls the motor 113 to quickly repeat to accelerate and decelerate the drum 124.

When the motor 113 repeats to accelerate and decelerate the drum 124, the laundry amount calculation unit 350 calculates the sum of currents in which the motor driver 310 applies to the motor 113 and obtains an average thereof, thereby calculating a laundry amount from a previously stored profile.

The laundry amount calculation unit 350 may calculate a laundry amount through a previously stored profile from the sum of currents in which the motor driver 310 applies to the motor 113 and a position of the motor 113 detected by the speed/position detection unit 330.

FIG. 10 is a graph illustrating a rotation speed of a motor to a time when calculating a laundry amount of a washing machine according to another exemplary embodiment of the present invention.

Referring to FIG. 10( a), according to another exemplary embodiment, when calculating a laundry amount, when the motor 113 accelerates the drum 124 from a first rotation speed ω₀ to a second rotation speed ω₁ and decelerates from the second rotation speed ω₁ to the first rotation speed ω₀, the motor 113 may constantly maintain the second rotation speed ω₁ between an acceleration segment and a deceleration segment during a predetermined time period.

Further, as shown in FIG. 10( b) or 10(c), according to another exemplary embodiment, acceleration may change in an acceleration segment or a deceleration segment, and an acceleration segment and a deceleration segment may be asymmetrically formed.

Referring to FIG. 10( b) or 10(c), acceleration a of some of an acceleration segment and acceleration −α of some of a deceleration segment may have the same magnitude. That is, constantly maintained some acceleration a in an acceleration segment that accelerates from the first rotation speed ω₀ to the second rotation speed ω₁ and constantly maintained some acceleration −α in a deceleration segment that decelerates from the second rotation speed ω₁ to the first rotation speed ω₀ may have the same magnitude.

The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being comprised in the present invention. 

1. A method of controlling a washing machine that calculates an amount of laundry housed within a drum rotated by a motor, the method comprising: accelerating the drum from a first rotation speed to a second rotation speed by enabling the motor to apply torque to the drum in a predetermined direction and decelerating the drum from the second rotation speed to the first rotation speed by enabling the motor to apply torque to the drum in an opposite direction; and calculating the amount of laundry from a sum of currents applied to the motor at the accelerating of the drum.
 2. The method of claim 1, wherein the first rotation speed and the second rotation speed are speeds at which laundry sticks to the drum and rotates.
 3. The method of claim 2, wherein the first rotation speed is 70 rpm, and the second rotation speed is 120 rpm.
 4. The method of claim 1, wherein accelerating the drum comprises repeatedly accelerating the drum, and thereafter the calculating the amount of laundry.
 5. The method of claim 1, wherein partial acceleration that accelerates the drum from the first rotation speed to the second rotation speed and partial deceleration that decelerates the drum from the second rotation speed to the first rotation speed have the same magnitude.
 6. The method of claim 5, wherein a magnitude of the partial acceleration is 20 rpm/s.
 7. The method of claim 1, wherein calculating the amount of laundry comprises calculating the sum of currents applied to the motor and the amount of laundry from a position of the motor.
 8. The method of claim 1, wherein accelerating the drum comprises accelerating the drum to the second rotation speed, maintaining the drum at the second rotation speed, and decelerating the drum to the first rotation speed.
 9. A washing machine comprising: a rotatable drum that receives laundry; a motor that rotates the drum; a motor driver that controls the motor by applying a current to the motor to accelerate the drum from a first rotation speed to a second rotation speed by enabling the motor to apply torque to the drum in a predetermined direction and to decelerate the drum from the second rotation speed to the first rotation speed by enabling the motor to apply torque to the drum in an opposite direction; and a laundry amount calculation unit that calculates an amount of laundry housed to the drum from the sum of currents which the motor driver applies to the motor.
 10. The washing machine of claim 9, wherein the first rotation speed and the second rotation speed are speeds at which laundry sticks to the drum and rotates.
 11. The washing machine of claim 10, wherein the first rotation speed is 70 rpm, and the second rotation speed is 120 rpm.
 12. The washing machine of claim 9, wherein the motor driver controls the motor to repeatedly accelerate and decelerate the drum.
 13. The washing machine of claim 9, wherein partial acceleration in which the motor accelerates the drum from the first rotation speed to the second rotation speed and partial deceleration in which the motor decelerates the drum from the second rotation speed to the first rotation speed have the same magnitude.
 14. The washing machine of claim 13, wherein a magnitude of the partial acceleration is 20 rpm/s.
 15. The washing machine of claim 9, wherein the laundry amount calculating unit stores the sum of currents corresponding to various laundry amounts as a profile and calculates the laundry amount using the profile.
 16. The washing machine of claim 9, wherein the motor driver accelerates the drum to the second rotation speed, maintains the drum at the second rotation speed, and decelerates the drum to the first rotation speed. 